Please try with the below code snippet.
HTML
<input id="datepicker" />
<input type="button" value="set date" onclick="setdateInDP()">
JS
<script type="text/javascript">
$(document).ready(function () {
function onChange() {
alert("Change :: " + kendo.toString(this.value(), 'd'));
}
$("#datepicker").kendoDatePicker({
change: onChange
});
});
function setdateInDP() {
var datePicker = $("#datepicker").data("kendoDatePicker");
var previousDate = new Date(datePicker.value());
previousDate.setDate(previousDate.getDate() - 1);
datePicker.value(previousDate);
$("#datepicker").data("kendoDatePicker").trigger("change");
}